IAC Red Set Science Bee Practice Test

Light cannot escape due to extreme gravity describes a black hole. The gravity is so intense that the escape velocity at a boundary reaches or exceeds the speed of light, so any light crossing that boundary—the event horizon—gets trapped. This makes the region effectively invisible from the outside, even though matter can still be drawn in and interact nearby. Nebulae are just clouds of gas and dust through which light travels freely; white dwarfs are extremely dense stars, but light can still escape from them; quasars are extremely bright centers of distant galaxies powered by accretion onto a black hole, but light escapes from the surrounding regions, not from an area where nothing can escape.